Users cannot place Railcraft tracks

[Galatamon]

I'm running a 3.1.3 server, and right now only OPs can place Railcraft tracks. Users have no problems with standard minecart tracks, but any of the special Railcraft rails disappear from both the world and their inventories upon placement. I don't know if this is a permissions issue or just a reason I should have held off on the 3.1.3 update, but I can't figure it out.

I'm using PEX; here's my permissions.cfg: http://pastebin.com/SufUfT8f